Conventionally, in an image sensing apparatus such as an electronic camera which converts an optical image of an object into electrical signals and records the signals as image data on a recording medium, the image sensing operation has been performed as described below.
First, when an image sensing/recording command is inputted by a switch (SW) and the like, a shutter is driven to expose an image sensing device, and then image signals accumulated in the image sensing device are read out after exposing the image sensing device for a proper period. The image signals from the image sensing device are converted into image data by an A/D converter and stored in a memory. Here, “RAW image data” refers to image data, obtained from the image signals from the image sensing device, which has not undergone image processing such as lossy compression.
After that, the RAW image data stored in the memory is read out again, and necessary signal processings are performed for the image based on a predetermined image quality setting to generate image data composed of R, G, and B values, for example. Lossy compression typified by JPEG (Joint Photographic Experts Group) coding is then performed for the image data to generate compressed image data, and the compressed image data is stored in a recording medium (the recording format is hereinafter referred to as an lossy compression format). In this way, a limited recording capacity of a recording medium is efficiently utilized.
In a conventional electronic camera, the compressed image data is expanded and the size of the image is changed (resized) to be suitable for display on a display unit, and then the sensed image is displayed on the display unit so that the sensed image can be viewed immediately after it is sensed. Further, after sensing an image/images, a playback operation is executed by changing the operation mode of the electronic camera to a playback mode. In the playback mode, the compressed image data is also expanded and resized to be displayed on the display unit.
Since the image sensing operation and the playback operation are performed as described above in a conventional electronic camera, a desired image may not be obtained when an image processing parameter such as image quality setting used for image processing is improper, that is, when a predetermined image quality setting and the like are not suitable.
There is also a problem that sufficient image quality may not be obtained when the image is playbacked, if lossy compression has been performed on image data. Furthermore, there is also a problem that, even if uncompressed image data is recorded on a recording medium, it may be difficult for a user to perform image processing on the uncompressed image data read out from a recording medium because processing such as white balancing has been performed at the above-mentioned process upon generating image data by performing signal processing on RAW image data.
One of formats for recording a sensed image to solve the above-mentioned problems is RAW format in which RAW image data, digital data of respective pixels read out from an image sensing device, is stored in a recording medium as it is. The RAW format can be said to be an advantageous recording format which provides a user with freedom of performing image processing after sensing an image.
However, RAW image data is not compressed or, if compressed, in a lossless compression format of low compression rate. Therefore, there is a problem in that, as pixel density of an image sensing device is increased and precision of an A/D converter is improved (increase in the number of bits) recently, RAW image data of one image increases in amount, thereby making it inconvenient to record the data in a capacity-limited recording medium. One way to cope with the increase in data amount is that a user carries a mass storage recording medium or multiple recording media. However, a cost burden on the user is naturally caused and longer time required for recording impairs comfortable image sensing activity.
As a countermeasure to the above-mentioned problem, an invention is proposed; wherein image quality settings are set as desired after RAW image data is stored in a memory by an image sensing operation; the RAW image data in the memory is read out; and then image processing based on the image quality settings is performed on the read RAW image data and a processed image is displayed on a display unit for confirmation (see Japanese Patent Laid-Open No. 2001-251551, for example). If the displayed image is not a desired one, the image quality settings are set again, and signal processing such as image processing based on the image quality settings is performed on the RAW image data and the processed image is displayed on the display unit for confirmation. If a desired image is obtained, the image data of the processed image is recorded onto a recording medium.
However, in an electronic camera in which an image associated with image data obtained by performing signal processing such as image processing based on image quality settings is displayed and confirmed, and then the signal-processed image data is recorded onto a recording medium, the image quality settings must be set for each image sensing operation. Furthermore, if a desired image is not obtained, the image quality setting, the signal processing and the image confirmation must be repeated. This requires a long time from image sensing to recording of image data, and therefore a long time before the camera becomes ready for the next image sensing operation, thereby causing missing of an image sensing opportunity.